Abstract

Based on combined x‐ray and neutron‐diffraction data, an inference for the coexistence of the B2(CsCl) and structures in the TiNi‐II phase is made. Other experimental evidence indicates the proportion of the B2 to structures to depend critically on the thermal and mechanical history of the alloy. Through a mechanism of an inhomogeneous‐but‐cooperative atomic shear in the direction and a factor sequence, in the (110)B2 plane, the B2 and structures transform into abd P6/mstructures, respectively, during the TiNi‐II to TiNi‐III martensitic transformation. Subsequent submicrotwinning at atomic level of the structure leads to the P1 structure. Therefore, the TiNi‐III (``martensite'') phase may consist of the , P1, and P6/mstructures.